Drop-back type selector



1958 i E. H. GATZERT 2,847,510

DROP-BACK TYPE SELECTOR Filed April 18, 1955 7 Sheets-Sheet 1 SWITCH DIOO Us THROUGH I I I00 A T IoI I I02 RI RPJ MON.A A I 1-LIO0 I I LINE CIRCUIT I LcI P03 TO CONNECTOR I Io4 MULTIPLE APPEARANCE I LINE FINDER cIoo 1 LFI I I gg r E:

l v I06 I I-Is A .41 l07a I I I I I I l l I I MO'NB A l 1 v I I l I I I I I I INVENTOR. ERNEST H. GATZERT A ENT 1958 E; H. GATZERT 2,847,510

i DROP-BACK TYPE SELECTOR Filed April 18, 1955 v 7 Sheets-Sheet 2 SEL LIS E. H.. GATZERT DROP-BACK TYPE SELECTOR Aug. 12, 1958 Filed April 18, 1955 7 SheetsSheet 3 RELEASE DIGIT REGISTER I 3|IO I I HUNT ASSIST 330 I PRIMARY DELAY 320 I I DELAY 3IO I CALLING BRIDGE 390 I I SEL us Aug. 12, 1958' E. H. GATZERT 2,847,510

" DROP-BACK TYPE SELECTOR Filed April 18, 1955 7 Sheets-Sheet 4 1958 E. H. GATZERT 2,847,510

- DROP-BACK TYPE SELECTOR Filed April 18, 1955 7 Sheets-Sheet 5 DIGIT DIGIT SERVICE REGISTER 2 REGISTER 3 RESTRICTING s00 SIG 550 wso v-r I I i I I I T so m 5g I I I V 522 PON42 I I I TO BUSY PON43 ITONE. souRcE I l I I I I SEL LIS I I I l I l I I l I I I I I I I l I I I I I I I Aug. 12, 1958 E; H. GATZERT DROP-BACK TYPE SELECTOR Filed April 18, 1955 7 Sheets-Sheet 6 SECOND REGISTER TIMING TO I INTER.

1958 E. H. GATZERT 2,847,510

DROP-BACK TYPE SELECTOR Filed April 18, 1955 7 Sheets-Sheet 7 T 7 TO FINDER MULTIPLE APPEARANCE LINE CIRCUIT LocAL 8. TOLL L 700 CONNECTOR LTC u (aDIGIT) 2" LEVEL NLEVEL TO OPERATOR TRUNK TERMINATIONS (M LOCAL OFFICE INC. SELECTOR IIIIIIIIII 7 EE? TOLL SELECTOR TOLEZZTORWIIIIITII TOLL SWITCHING OFFICE DISTANT OFFICE United States Patent DROP-BACK TYPE SELECTOR Ernest H. Gatzert, Rochester, N. Y., assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application April 18, 1955, Serial No. 502,055

7 Claims. (Cl. 179-18) The present invention relates to telephone systems in general and more particularly to a selector of the dropback type which is adapted for use in such a system.

At the present time it is the practice to provide a drop-back type local selector suitable for use in a socalled 2-5 switching system such as the selector shown and described in application Serial No. 424,846, titled Local First Selector Circuit, filed April 22, 1954, and assigned to the same assignee as the present application. The selector is capable of absorbing a plurality of unlocking signals which represent a local office code following the absorbing of the office code or unlocking signals, the selector is unlocked so that a hunting operation is carried out within the level selected responsive to the receipt of the next directive signal. In such a selector it is also the practice to provide means operative responsive to a first signal identical to the last of the series of oifice code signals for unlocking the selector immediately so that a connection may be extended through the selector without the transmission of the entire unlocking oifice code signal. In the case of an ofiice code in which the second and third signals to be absorbed are identical, the problem is presented of making the signal absorbing or registering apparatus within the selector differentiate between the second signal of the ofiice code transmitted 'as a part of the unlocking code and the third oifice code signal transmitted as a single unlocking signal.

Accordingly, it is an object of my invention to provide a new and improved drop-back type selector.

Another object of my invention is to provide a selector which unlocks responsive to the receipt of an unlocking code of signals comprising successive signals in which the last two signals are alike and different from the first; and which unlocks responsive to the receipt of another unlocking signal comprising a single signal identical to the last of the successive signals of the unlocking code.

In order to accomplish these and other objects, I provide in the preferred embodiment of my invention a telephone system comprising a local first selector having a set of wipers; the wipers may be directed by primary means to any one of a plurality of levels including first and second particular levels. Secondary means may be thereafter operative for advancing the wipers within any one of the selected levels in a hunting operation.

First registering means is provided for recording a first primary movement to the first level and second and third primary movements to the second level which are caused by the receipt of a set of unlocking directive signals and the consequent operation of the primary means; the three successive recording operations constitute an unlocking operation of the registering means. Each recording operation of the registering means is effective for causing releasing means to operate whereby the wipers are restored to their normal position at the conclusion of each of the signals. A separate other registering means is operative responsive to a first primary movement of the wipers to the second particular level for causing an unlocking operation of the registering means.

Patented Aug. 12, 1958 ICC After an unlocking operation of the registering means; the selector is prepared to receive a directive signal which is effective to cause the wipers to select any one of the levels to which the selector has access. In order to cause the wipers to hunt within such a level, means operative responsive to the unlocking operation of the registering means and to a subsequent operation of the primary means is effective for thereafter causing means for controlling hunt starting means to operate. The operation of the hunt starting means is effective for causing the secondary means to operate and thus initiate a hunting operation in the level selected by the movement of the wipers subsequent to the unlocking operation of the registering means.

Further objects and advantages of my invention will become apparent as the following description proceeds, and features of novelty which characterize the invention will be pointed out with particularity in-the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawings in which:

Fig. 1 shows a schematic representation of a subscribers line, a line circuit and a line finder, and in detail a part of a local first selector LlS;

Figs. 26 show the remainder of the local first selector LlS;

Fig. 7 shows a schematic representation of a local and toll connector LTC, an incoming selector IS-1 as well as a subscriber station D in a distant oflice together with toll switching ofiice apparatus; and

Fig. 8 shows the relationship of Figs. l-7.

The apparatus referred to in the following description is made to function from power supplied from a source such as a battery. The most positive plate of the battery is connected to ground and is referred to hereafter as ground and in the drawings as the most negative ungrounded plate of the battery is referred to as battery and in the drawings as Because the present invention lies in selector L1S and because the other apparatus with which the selector is used functions in any of a number of ways well understood to those skilled in the telephone art, the description of the operation of the other apparatus is set forth only in general terms except in those instances in which the other apparatus contributes directly to the operation of the selector.

In the system contemplated, a call from a distance office station, such as C shown in Fig. 7, may be completed to a station such as B in the ofiice hereinafter referred to as the local ofiice and which includes the link comprising line finder LF and local first selector LIS shown in Figs. l6. A connection is extended from station C by means not shown to the toll switching apparatus comprising selectors such as TS1, TS2 and T83. The subsequent transmission of an oifice selecting code comprising a plurality of directive signals or digits from station C is effective for consecutively advancing the selectors TS1, TS2 and T83 to further extend the connection from station C to the terminals of a trunk such as 1T1 which terminates in an incoming selector such as IS-l in the local ofiice. Assume that the above-described ofi'ice code comprises three signals or digits in which the second and third signals are alike and are different from the first signal. An example of such a code is the digits 4 3 3 which is hereafter used for purposes of demonstration as being the code of the local office.

After a connection has been extended from station C to selector IS-l, further directive signals comprising the line code or selecting digits which are subsequently transmitted over the built-up connection are etfective to step the switches in the local ofiice to complete the connection to the called station. The first of these line code signals such as the digit 9 advances selector 18-1 to the ninth level; the selector thereafter hunts in the ninth level for and thereafter seizes an idle local and toll connector, such as LTC. Transmission of the remaining line code signals of stationB to the local and toll connector LTC is efiective to advance the wipers of the connector to the terminals of line circuit LC2 on which the line of station B is terminated.

Thus it is seen that three office code signals followed by a number of line code signals must be transmitted from the calling station in the distant oifice in order to extend a connection from the distant ofiice station C to local office station B by way of the toll switches. In a multioffice system of the type referred to in the preceding paragraphs, it is necessaryto assign such a combination of oflice selecting and line selecting codes to each station in the system in order to create a uniform numbering scheme.

To extend a call from a station such as A within the local ofiice to a station within the same office such as B over a switch train comprising a local first selector L1S and a local and toll connector such as LTC, it is necessary to make it possible for subscribers to dial all of the otfice and line code signals of the called station in order to preserve the uniform numbering scheme throughout each ofiice within the system. It is pointed out that these ofnce selecting digits are not used to extend the connection from the calling to the called line within the local office. Therefore, in order to speed the selecting process the selector is arranged so that it is possible to dial only the last signal or digit of the office code followed by the line code of the called subscribers line. The last digit of the ofiice code serves to unlock the selector so that the wipers are advanced within the level selected by the next succeeding signal, in the case illustrated, level 9.

To originate a call from a station wihin the local office, such as A, to another local ofiice station, such as B, the telephone at station A is removed from its hookswitch to energize line circuit LC1. The energization of line circuit LC1 is effective to cause line finder LF1 to be advanced by means not shown to the terminals in the finder multiple, thereby extending a connection from station A to the conductors of line finder LF1 which are shown collectively as C100 and to the local first selector L1S which is associated with line finder LFI. Extension of the connection from station A to selector L1S is effective to complete an operating circuit for calling bridge relay 300 and for energizing the transmitter at station A as follows: from ground through break contacts 321, primary off-normal contacts PON43, break contacts 522, 502, 341, overflow contacts OF41, the upper winding of calling bridge relay 300, break contacts 101, tip conductor T, one of the conductors of line finder LF and line L100, the pulsing contacts D100 of the station A dial, the other conductor of line L100 and line finder LP, the ring conductor R, contacts 103, and the lower winding of calling bridge relay 300 to battery. Relay 300 thereupon operates and is thereafter effective for repeating signals comprising trains of impulses caused by the systematic opening and closing of contacts D100 of the dial at station A. Operation of relay 300 is effective to operate release delay relay 310 by completing a circuit for energizing the winding of relay 310 from ground at break contacts 631 and make contacts 302; the operation of relay 300 is also effective to operate primary delay relay 320 from ground through break contacts 631, make contacts 302, primary off-normal contacts PON41, and the upper winding of relay 320 to battery. Relay 320 thereupon operates.

Operation of relay 310 is effective to supply a ground connection to the sleeve conductor S of the line finder LP to mark that finder and line circuit LC1 as being busy to other equipment within the office at make contact 413.

Operation of primary delay relay 320 is, efiectiveto transfer the operating loop of calling bridge relay 300 from the above described ground connection to a low impedance tone source to supply a dial tone to the receiver at station A at make contacts 322 to indicate to the station A that the local first selector LlS is ready to receive directive signals from the dial at station A.

Transmission of a train of impulses from the contacts D at station A is effective to release and reoperate calling bridge relay 300 in response to each individual impulse in the train. Release delay relay 310 being a slow release type remains operated during the time that its operating circuit is opened at make contacts 302 and is consequently held in its operated condition throughout the transmission of the train of impulses. Responsive to each release of relay 300, a circuit is completed for operating the means comprising primary magnet PM40 for advancing the wipers of selector L1S in the primary direction as follows: from ground through break contacts 631 and 303, make contacts 312, make contacts 325, and the winding of magnet PM40 to battery. Each operation of magnet PM40 is effective to advance the wipers W5.0-W53 one step to place them opposite one of the levels to which the selector L1S has access. Upon the reoperation of relay 300, the above-traced operating circuit for magnet PM40 is opened at break contacts 303 so that the magnet PM40 is deenergized. The completion of the above-traced operating circuit for magnet PM40 also completes aholding circuit for primary delay relay 320 by energizing the lower winding of relay 320 in parallel with the magnet PM40. Relay 320 being a slow release type is thereby held in its operated condition throughout the. stepping operation of primary magnet PM40.

Means comprising primary off-normal springs PON41 are operated responsive to the advance of the. wipers W50-W53 away from their normal position in the primary direction. As a result, the above describedoperating circuit of primary delay relay 320 is opened. At the conclusion of a'train of impulses, when calling bridge relay 300 comes to rest in its operated condition, the above described holding circuit for relay 320 is opened at break contacts 303. Primary delay relay 320 is thereby released after a train of impulses has been repeated by relay 300.

In the event that the subscriber at station A has elected not to dial all the directive signals which comprise the office code of the local oflice, he causes the dial contact D100 at station A to transmit the final signal of the ofiice code (the digit "3 in the present example) followed by the line selecting code of the called station E. Thus, the first signal transmitted causes magnet PM40 to advance Wipers W50W53 to the thirdlevel. Level marking means associated with the selector comprising auxiliary wipers W60 and W61 are advanced one step for eachoperation of primary magnet PM40 and have access to terminals to which various level indicating wiring, such as Z, is connected. level has been selected by the first directive signal, so that the level marking means comprising the wiper W60 is effective for energizing a first means comprising relay 620 over the following circuit: ground at make contact'413, break contacts 108 and 324, wiper W60, the Z wiring, break contacts 445, 609, 618 and 625, the winding of relay 620, break contacts 623 and RM41 to battery. Relay 620 thereupon operates and completes for itself a locking path from battery through make contacts 624, the winding of relay 620, make contacts 626, break contacts 108, and make contacts 413 to ground.

The operation of the first means is effective for causing an unlocking operation of a registering means comprising first, second and thirdcontrolling means in the form of digit registering relays 1, 2 and 3 (340, 500 and 510, respectively) in the manner next described. It is to be noted that the unlockingoperation of the registering In the present case, the third means takes place when relays 340, 500 and 510 are all operated.

Operation of relay 620 with the relays 340, 500 and 510 in normal condition is elfective for operating digit register 2 relay by completing the following operating circuit: from ground through make contacts 413, break contacts 108, 324,wiper W60, Z wiring, make contacts 627, break contacts 619a, secondary off-normal contacts SON41, the winding of relay 500, and break contacts 505 and RM41 to battery. Operation of relay 500 is effective for completing a locking circuit for itself from battery through make contacts 506, the winding of relay 500, make contacts 503, break contacts 512, 108, make contacts 413 to ground.

The operation of relay 500 is effective for completing an operating circuit for digit register 3 relay 510 from ground through make contacts 413, break contacts 108 and 324, wiper W60, Z wiring, break contacts 445, make contacts 608, the winding of relay 510, and break contacts 516 and RM41 to battery. Relay 510 thereupon operates and completes a locking circuit for itself from battery through make contacts 517, the winding of relay 510, make contacts 515, contacts 108 and 414 to ground.

The operation of relay 510, is effective to cause digit register 1 relay 340 to operate by completing the following circuits: from ground through make contacts 413, break contacts 108, contacts PM41, make contacts 513, 503 and 514, the winding of relay 340 to battery. Relay 340 thereupon operates and completes a locking circuit for itself at contacts 344 which includes in series primary magnet interrupter contacts PM41, contacts 108 and 413 toground.

Operation of relay 510 is also effective to open the above referred to operating and locking circuits for relay 500 at contacts 619a and 512, respectively. However, the operation of relay 510 is also effective to complete an auxiliary locking circuit for relay 500 through make contacts 503 and 513, interrupter contacts PM41, thence to the same supply of ground as used for locking relay 340.

Operation of the first controlling means comprising relay 340 iseffective for energizing the releasing means comprising magnet RM40 by completing the following circuit: from ground through make contacts 413, break contacts 108 and 324, wiper W60, Z wiring, make contacts 449, 609a, 447 and 415, break contacts 2090, the now-closed primary off-normal make contacts PON44, and thewinding of release magnet RM40 to battery. Operation of magnet RM40 is effective in the well known manner to restore the wipers W50-W53 and auxiliary wipers W60 and W61 to their normal positions. An unlocking operation of the registering means comprising relays 340, 500 and 510 has been brought about.

The subscriber at station A next causes the dial contacts to transmit a directive signal which is utilized as the first of the line code selective signals; the signal is effective to cause magnet PM40 to advance the wipers W50-W53 to the ninth level of the selector in the above described manner. Responsive to the unlocking operation of the registering means and to the operation of primary magnet PM40, the holding circuit for relays 340 and 500 is opened at interrupter contacts PM41 on magnet PM40. Relays 340 and 500 thereupon release to render hunt-start controlling means comprising contacts 607 on relay 500 to be effective to energize secondary moving means comprising hunt assist relay 330 and secondary magnet SM40 in the manner next described.

When the conclusion of the primary movement which follows the unlocking operation of the registering means is indicated by the release of primary delay relay 320, the following circuit is completed by controlling means comprising contacts 607 on digit register 2 relay 500: from ground through make contacts 413, break contacts 108, make contacts 515, the now-closed break contacts 607 on relay 500, break contacts 426, secondary offnormal contacts SON43, overflow contact OF31, secondary magnet interrupter contact SM41, the winding of hunt assist relay 330, and release magnet interrupter contacts RM41 to battery. Relay 330 thereupon operates and completes an energizing circuit for the secondary magnet SM40 from ground at contacts 413, break contacts 109a, make contacts 331, and the winding of magnet SM40 to battery.

The operation of magnet SM40 is effective to advance the wipers W50-W53 one step in the secondary direction within the selected level. Wipers W50W53, advanced one step in the secondary direction, engage the first of the terminals within any one of the selected levels (level 9 in the present example). Further stepping of wipers within the level is dependent upon the busy or idle condition of the equipment terminated on the set of conductors which have been engaged by the wipers. Testing means comprising test wiper W52 control the further advance of the switch in the manner next described. Following the completed step to the first or any other set of terminals within a selected level, the test wiper W52 is effective for extending a connection from the test conductor of the set of Wipers with which engagement has been established to the secondary means comprising the hunt assist relay 330 over the following circuit: from the test conductor of the set of wipers to which the wiper set has been advanced, through wiper W52, sleeve conductor S, break contact 105, make contact 311, overflow contact OF31, secondary interrupter contact SN41, the winding of relay 330, and release magnet interrupter contact RM41 to battery. A busy condition of the set of conductors under test is indicated by the presence of a ground potential on the test conductor which is engaged by wiper W52. Therefore, a busy condition is elfective to cause the operation over the above traced test circuit of hunt assist relay 330 in the event that the set of conductors'under test is in busy condition. Operation of the hunt assist relay is effective in the previously described manner to energize the secondary magnet SM40 to reoperate the magnet and thereby advance the wipers W50--W53 one step further Within the selected level.

Operation of hunt assist relay 330 is effective to extend ground from make contacts 413 through break contacts 109a, make contacts 331 to the winding of secondary magnet SM40 to battery. Secondary magnet SM40 thereupon operates to open the interrupter contacts SM41. Opening of the contacts SM41 is effective to open the above described operating circuit for hunt assist relay 330 whereby relay 330 is subsequently released. Release of relay 330 is effective to open the operating circuit of magnet SM40 to deenergize and thereby release the secondary magnet SM40.

The movement of the wipers away from their secondary normal position is effective to operate secondary off-normal contacts such as SON42. When an idle set of conductors is encountered by wipers W50-W53 a circuit is completed for operating switchthrough relay from ground at make contacts 413, through the winding of relay 100, secondary off-normal contacts SON42, overflow contacts OF31, secondary interrupter contacts SM41, the winding of relay 330, release magnet interrupter contacts RM41 to battery. The resistance of relay 100 is sufficiently high so that relay 330 is prevented from being operated at this time.

Operation of switchthrough relay S100 is effective to disconnect the windings of the calling bridge relay 300 from the above described operating loop and to extend the metallic connection from the calling station A through contacts 102 and 104 of relay 100 to the connector switch such as LTC to which the wipers W50-W53 have been extended. Connector LTC is theEiip on seized; seizure of connector LTC is effective to cause well known means to pass back holding ground for the switchthrough relay 100 over wiper W53 through make contacts 106, so that relay 100 continues to be operated throughout the remainder of the call. Upon its disconnection from the calling loop, relay 300 is released to release relay 310 by opening the operating circuit of the latter relay at contacts 302. Operation of the switch through relay is also effective to open the holding circuit of digit register 3 relay 510 at break contacts 108 thereby releasing the registering means to its normal condition.

The subscriber at calling station A thereupon manipulates the dial at the station so that contacts D100 thereafter transmit the remainder of the called line code to the remaining switches in the local ofiice link, such as connector LTC, to cause the latter to be advanced by means well known in the telephone art to the terminals of the called line L700 and to subsequently establish a connection from the calling station A to the called station B.

At the conclusion of the call, release of the connection is under the control of the calling station A by any of a number of well known means A release condition is indicated to selector L1S by the removal of holding ground from wiper W52 thereby releasing switchthrough relay 100. In the case of selector LlS, release of relays 100 and 310 is effective to complete an energizing circuit for release magnet RM40 as follows: from ground through break contacts 416 and 2090, make contacts PON44 and SON42, and the winding of magnet RM40 to battery. The operation of magnet RM40 is effective to release Wipers W50W52 to their normal position. The other apparatus including line circuit LC1, line finder LP, and connector LTC are all released by well known means and are thereby freed for use in subsequently placed calls from any station within the local ofiice.

Returning to the point in the previous description at which the first impulse is transmitted from the contact D100 of the station A dial and assuming that the subscriber at station A elects to dial the oflice code followed by the line code of the called station B, the operation of the selector LlS is next described. The first of the directive signals in the example chosen, the digit 4, is effective for directing the wipers'W50W54 to a first particular (fourth) level. At the conclusion of the transmission of the signal, the previously described level responsive means comprising wiper W61 is effective for completing a circuit for energizing digit register 1 relay 340 as follows: from ground, through wiring V, wiper W61, break contacts 511a, 323, make contacts 301, break contacts 109, make contacts 343, and the winding of digit register 1 relay 340 to battery. Relay 340 thereupon operates and completes for itself a locking circuit from battery to the winding of relay 340, make contact 344, primary magnet interrupter contacts PM41, break contacts 108 and make contacts 413 to ground. T heoperation of relay 340 is effective to record the first primary movement of the selector to the second particular level to which the wipers W50--W53 have access and to prepare at contacts 446 an operating circuit for digit register 2 relay 500. Operation of relay 340 is further effective to prevent the operation of the first means comprising relay 620 by opening the previously traced operating circuit of that relay at break contacts 445 to render the first registering means thereafter inoperative. The first recording operation of the registering means as indicated by the operation of relay 340 is effective to operate the releasing means comprising release magnet RM40 by closing the following circuit: from ground through make contacts 413, break contacts 108 and 324, wiper W60, wiring N, make contacts 447 and 415, break contacts 2090, make contacts PON44, and the Winding of release magnet RM40 to battery. The wipers W50,-W53 are restored to normal position, thereby reclosing the operating circuit for pulse delay relay 320 at contacts PON41.

The registering means is thereupon in condition to carry out a second recording operation.

The operation of digit register 1 relay 340 and the subsequent direction of the wipers W50W53 to the second particular level (in the example chosen, the level 3) in response to the dialing of a second of the otnce selecting signals 433 is effective to cause the level marking means comprising wiper W60 to'cause a second :recording operation of the registering means. The following circuit is completed upon the release of primary delay relay 320: from ground through make contact 413, break contacts 108 and 324, wiper W60, the Z wiring, make contacts 446, secondary off-normal contacts SON41, the winding of relay 500, break contacts 505, release magnet interrupter contacts RM41 to battery. Relay 500 thereupon operates and completes for itself a locking circuit from battery through make contacts 506, the winding of relay 500, make contact 503, break contacts 512, break contacts 108, make contacts 413 to ground.

Operation of the digit register 2 relay 500 is effective for further opening the operating circuit of the relay 620 at contacts 609 and thereby further rendering the pre viously referred to first means ineffective. Operation of relays 340 and 500 constitutes a second recording operation of the registering means. The operation of relay 500 is also effective forpreparing digit register 3 relay for operation at contacts 608.

Operation of the digit register 1 relay 340 and digit register 2 relay 500 is effective responsive'to the advancement of the wipers'to the second particularlevel (level 3 in the example chosen here) to reenergize the release magnet RM40 over the following circuit:- from ground through make contact 413, break contacts 108 and 324, wiper W60, wiring Z, make contacts 449 and 415, break contacts 2090, primary off-normal contacts PON44, the winding of magnet RM40 to battery. Release magnet RM40 thereupon operates to again restore the wipers W50W54 and auxiliary wipers W60 and W61 to their normal position. The operating circuit for relay 320 is again completed at now closed contacts PON41 to reoperate relay 320.

In response to the dialing of the third of the series of unlocking signals (the digit 3) of the oflice selecting code, wipers W50W53 are again advanced in the primary direction to the second particular'level (3); responsive to the operation of digit register 2 relay 500, theoperation of primary magnet interrupter contact "PM41 is effective for opening the above traced locking circuit of digit register 1 relay 340 at contacts PM41 to release digit register 1 relay 340. V

The operation of digit register.2 relay.500 is also effective for opening an alternate holding path for relay 340 around the primary magnet interrupter contact PM41 comprising a path through breakcontacts 512, 504 and 511 by. opening break contacts 504 in order to render the primary interrupter contact PM41 effective in the manner previously described.

At the conclusion of the dialing ofthe third unlocking signal of the office code and responsive to the operation of the level marking means which indicates the ad- Vance of the wipers W50W53 to the second particular level (3) and the release of relay 340, a circuit is completed for operating digit register 3 relay 510 over the following circuit: from ground through make contacts 413, break contacts 108 and 324, wiper W60, wiring Z, break contacts 445, make contacts 608, the winding of relay 510, break contacts 516, release magnet contacts RM41 to battery. Operation of relay'510- is effective to establish a locking circuit for itself from'battery through make contacts 517, the winding of relay- 510, 'make'contacts 515, break contacts 108, make contacts 413 to ground.

The operation of digit registerl and' digit register3 relays-500 and 510, respectively, is efiective to reestablish an operating circuit for digit register 1 relay 340 to ass /e 9 complete a third recording operation and an unlocking operation of the registering means. A circuit for operating relay 340 is completed as follows: from ground, through make contacts 413, break contacts Mitt, primary magnet interrupter contacts PMM, make contacts 5213, make contacts 503, make contacts 514, the winding of relay 340 to battery. Relay 34d thereupon reoperates and establishes a previously traced locking circuit for itself through make contacts 344. It is to be noted that the previously traced locking circuit of relay 5% is opened and a substitute locking circuit identical to the previously traced locking circuit for relay 340 is established and mo tended to the winding of relay 5% at make contact 514.

Operation of digit register 1 and digit register 2 relays 340 and 500, respectively, is effective to establish an operating circuit for release magnet RM ltl from ground at make contact 413, through break contacts 108, break contacts 324, wiper W60, wiring Z, make contacts 449 and 609a, make contacts 447 and 415, break contacts 209e, primary off-normal contacts PON44, and the winding of release magnet RM to battery.

The joint operation of relays 340, 500 and 510 constitutes an unlocking operation of the registering means. Subsequent operation of the primary magnet Pit/Mil to advance the wipers W50-W53 to the ninth level in an advance caused by the transmission of thefirst of the line code selecting digits is effective to operate primary magnet interrupter contacts PMM. The operation of the interrupter contacts PM l-l in combination with the unlocking operation of the registering means is effective a to open the previously described holding circuits for relays 340 and 500 which thereupon release. In response to the release of relay 500, the previously described hunt controlling means comprising the circuit controlled by contacts 607 is completed to start the switch to hunting in the secondary direction in the previously described manner. The call then proceeds in the previously described manner to its conclusion.

While I have shown and described a specific embodiment of my invention, other modifications will readily occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the specific arrangement shown and described and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What is claimed is:

1. In a selector comprising a set of wipers having a normal position and a plurality of levels of contacts disposed for engagement by said wiper set and including a particular level and other levels, means for transmitting directive signals for selectively moving said wipers in a primary direction to any one of said levels, means thereafter operative for advancing said wipers in a secondary direction within said any one level in a hunting operation, means operative in response to primary movements of said wiper set for restoring said wiper set to normal position, first means operative in response to each of a series of successive primary movements of said wiper set to certain of said levels including a first movement to one of said other levels and an intermediate movement to said particular level for operating said restoring means and for registering each of a series of movements and thereafter operative in response to a subsequent primary movement of said wiper set to said any one level for rendering said secondary means operative, other means operative in response to a primary movement of said Wiper set to said particular level for placing said first means in condition to render said secondary means operative, means operative in response to said first registering operation of said first means for rendering said other means inoperative, and said other means in operative condition and said first means in condition to render said secondary means operative being jointly effective for operating said restoring means, whereby said wiper set may be restored to said normal position following a .U rat) 10' first primary movement to said particular level and thereafter advanced within said particular level or within said any one level subsequent to said series of restorations to normal position and a corresponding number of registering operations of said first means have been carried out.

2. The system set forth in claim 1 wherein said first means is also operative in response to a subsequent operation of said primary means for operating said secondary means, whereby said wiper set is advanced Within said any one level selected by a primary advance of said wipers subsequent to said series of registering operations of said first means.

3. The system set forth in claim 1 wherein said first means is also operative in response to a subsequent operation of said primary means for operating said secondary means and said other means in operative condition and said first means placed in condition to render said secondary means operative are effective for operating said restoring means.

4-. In a selector comprising a set of wipers having a normal position and a plurality of levels of contacts disposed for engagement by said wipers including a first and a second particular level, means for transmitting directive signals to said selectors, means operative in response to the receipt of directive signals for moving said wiper set to any one of said levels, means operative in response to selected primary movements of said wiper set for restoring said wipers to said normal position, means for advancing said wipers in said any one level in a hunting operation, first means operative in response to each of a series of successive primary movements of said wiper set including a first movement to said first level and an intermediate movement to said second level for registering each of said movements and for operating said restoring means and thereafter operative in response to a subsequent primary movement of said wiper set to said any one level for operating said secondary means, other means operative in response to a primary movement of said Wipers to said second level for placing said first means in condition to render said secondary means operative, and means operative in response to a registering operation of said first means caused by a first primary movement of said wipe set to said first level for rendering said other means inoperative, whereby said wiper set may be advanced within said second level prior to said series of registering operations of said first means or within said any one level subsequent to said series of registering operations of said first means.

5. The system set forth in claim 4 wherein said other means in operative condition and said first means placed in condition to render said secondary means operative are effective for operating said restoring means, whereby said wiper set is restored to said normal position following a first primary movement to said particular level.

6. The system set forth in claim 4 wherein said first means is also operative in response to a subsequent operation of said primary means for operating said secondary means, whereby said wiper set is advanced within said any one level selected by a primary advance of said wipers subsequent to said series of registering operations of said first means.

7. The system set forth in claim 4 wherein said first means is also operative in response to a subsequent operation of said primary means for operating said secondary means and said other means in operative condition and said first means placed in condition to render said sec ondary means operative are effective for operating said restoring means.

References Cited in the file of this patent UNITED STATES PATENTS 1,883,680 Friendly Oct. 18, 1932 2,642,498 Riddell et al. June 16, 1953 2,721,902 Pharis Oct. 25, 1955' 2,748,194 GatZert May 29, 1956 

